U.S. patent number 7,759,903 [Application Number 11/725,554] was granted by the patent office on 2010-07-20 for battery voltage measurement circuit, battery voltage measurement method, and battery electric control unit.
This patent grant is currently assigned to Keihin Corporation. Invention is credited to Seiji Kamata.
United States Patent |
7,759,903 |
Kamata |
July 20, 2010 |
Battery voltage measurement circuit, battery voltage measurement
method, and battery electric control unit
Abstract
A voltage between both terminals of each unit battery is
amplified by a differential amplifier and is then converted by a
converter into a predetermined physical quantity that corresponds
to the voltage between both terminals of the unit battery. The
converted physical quantity is then level-shifted by a detection
circuit and is converted into a voltage on a reference potential of
the lowest electric potential of the battery assembly. A control
unit sequentially selects the converted voltages by a multiplexer,
generates serial digital signals by an A/D conversion, and then
transmits the serial digital signals to a control operation unit
via an isolation buffer circuit. It is, therefore, possible to
provide a battery voltage measurement circuit capable of measuring
a voltage of each of unit batteries constituting a battery assembly
with high accuracy by using a common measurement circuit in a
relatively simple and inexpensive configuration.
Inventors: |
Kamata; Seiji (Miyagi,
JP) |
Assignee: |
Keihin Corporation (Tokyo,
JP)
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Family
ID: |
38630507 |
Appl.
No.: |
11/725,554 |
Filed: |
March 20, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070285083 A1 |
Dec 13, 2007 |
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Foreign Application Priority Data
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Mar 23, 2006 [JP] |
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2006-081589 |
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Current U.S.
Class: |
320/134; 320/152;
320/132; 324/433 |
Current CPC
Class: |
G01R
31/3835 (20190101); G01R 31/396 (20190101) |
Current International
Class: |
H02J
7/00 (20060101); H02J 7/04 (20060101); H02J
7/16 (20060101); G01N 27/416 (20060101) |
Field of
Search: |
;324/433,434
;320/134 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-113182 |
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Apr 1999 |
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JP |
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2002-122643 |
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Apr 2002 |
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JP |
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2002-156392 |
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May 2002 |
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JP |
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2003-70171 |
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Mar 2003 |
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JP |
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Primary Examiner: Tso; Edward
Assistant Examiner: Omar; Ahmed
Attorney, Agent or Firm: Kratz, Quintos & Hanson,
LLP
Claims
What is claimed is:
1. A battery voltage measurement circuit that measures a voltage
between two electrodes of each unit battery in a battery assembly
having a plurality of unit batteries which are connected in series,
the battery voltage measurement circuit comprising: conversion
units each provided respectively to each unit battery to convert a
voltage between the two electrodes of each unit battery into
respective predetermined physical quantities; a level shifting unit
to convert the physical quantities converted by the conversion
units into voltages relative to a lowest electric potential of the
battery assembly, wherein the level shifting unit is directly
connected to the lowest electric potential of the battery assembly;
a measurement unit that processes and measures the physical
quantities converted by the conversion units with respect to each
of the unit batteries; and a power source, isolated from the
battery assembly, to supply power to the conversion units; wherein
the measurement unit sequentially outputs digital values
corresponding to the converted voltages based on the lowest
electric potential of the battery assembly with respect to the unit
batteries; and wherein each conversion unit includes a
voltage-current conversion unit that converts the voltage between
the two electrodes of each unit battery into a corresponding
magnitude of an electric current.
2. The battery voltage measurement circuit according to claim 1,
wherein the measurement unit includes an A/D conversion unit that
converts the voltage between both electrodes of the unit battery
into a corresponding digital signal.
3. The battery voltage measurement circuit according to claim 1,
wherein the conversion units each corresponding to each of the unit
batteries are formed into groups consisting of a predetermined
number of the conversion units, which are adjacent to each other;
each group is provided with a charge pump circuit; and the
conversion unit in each group operates with a power supply from the
charge pump circuit associated with the each group.
4. The battery voltage measurement circuit according to claim 3,
further comprising a DC/DC converter that is electrically insulated
from the battery assembly and is used as an power source for each
charge pump circuit.
5. The battery voltage measurement circuit according to claim 1,
wherein each conversion unit includes a voltage-frequency
conversion unit that converts the voltage between the two
electrodes of each unit battery into an alternating signal having a
corresponding frequency.
6. The battery voltage measurement circuit according to claim 1,
further comprising: a control operation unit that is electrically
insulated from the battery assembly; and a transmitting unit that
electrically transmits the digital value corresponding to the
voltage between the two electrodes of each unit battery from the
measurement unit into the control operation unit while keeping
insulation between the battery assembly and the control operation
unit.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
This application claims the foreign priority benefit under Title
35, United States Code, .sctn.119 (a)-(d), of Japanese Patent
Application No. 2006-81589, filed on Mar. 23, 2006 in the Japan
Patent Office, the disclosure of which is herein incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for measuring a voltage
of each of cells constituting a battery assembly having a large
number of cells, which are connected in series.
2. Description of the Related Art
In hybrid vehicles, electric vehicles, fuel-cell vehicles or the
like, it has become common to configure a high-voltage battery
assembly by connecting in series a plurality of unit batteries
including rechargeable batteries or fuel cells in order to reduce
the loss due to wiring resistance or reduce the size of a switching
element. In the case that a fuel cell is used, for example, a cell
voltage of a fuel cell is around 1 volt, and therefore generally
several hundreds of cells are connected in series to provide a
required high voltage. In such a case, when one of unit batteries
has a trouble and operates with an extreme low or high voltage, the
unit battery having a trouble can cause corrosion or insufficient
voltage resistance, which can result in the breakage of a whole
battery assembly. Therefore, when such a battery assembly is used,
a voltage of one unit battery or voltages of a plurality of unit
batteries are sequentially scanned at a time to measure and monitor
a voltage, thereby making it possible to promptly deal with any
trouble.
There have been known examples for monitoring a voltage as
mentioned above. Japanese Laid-open Patent Application Hei
11-113182 (Paragraph [0017]; FIG. 1) discloses an example for
detecting a voltage of each of unit batteries by different
differential amplifiers by using a bottom terminal as a reference.
Japanese Laid-open Patent Application No. 2003-70171 (Paragraph
[0017]; FIG. 1) discloses an example for detecting a voltage of
each of batteries by using a virtual ground, which has the same
electric potential as that of a midpoint of an battery assembly, as
a reference.
Japanese Laid-open Patent Application No. 2002-156392 (Abstract;
FIG. 1) discloses a so-called flying capacitor technique. In this
technique, a voltage of each unit battery is sequentially applied
to a flying capacitor through a pair of multiplexers, and then the
multiplexers are shut off to sample and hold the voltage of the
unit battery. Then, each end of the flying capacitor is
electrically conducted to a voltage detection circuit via an analog
switch, which is designed to output an electrical potential of a
capacitor, so that a potential difference of the flying capacitor,
i.e. a storage voltage of the flying capacitor is detected by the
voltage detection circuit.
In an example disclosed in Japanese Laid-open Patent Application
No. 2002-122643 (Paragraph [0044-0048]; FIG. 1), a voltage of each
unit battery is input to a pair of input terminals of a first stage
differential amplifier via a pair of multiplexers. Then, the first
stage differential amplifier differentially amplifies a voltage on
a reference potential of a bottom potential of a battery assembly.
An output voltage of the first stage differential amplifier is
amplified by a subsequent stage differential amplifier by using a
ground potential of a vehicle body as a reference, and then an
output voltage of the subsequent stage differential amplifier is
A/D converted.
In the above-mentioned systems in Japanese Laid-open Patent
Applications Hei. 11-113182 and No. 2003-70171, however, a
reference voltage of a first stage differential amplifier or a
converter, which detects an input voltage of a unit battery, is a
bottom terminal or a virtual ground having the same potential as
that of a midpoint of a battery assembly. In such a case, a voltage
to be input to a first stage amplifier or a converter increases.
Therefore, it is difficult to obtain a large gain, and the accuracy
of the voltage detection is deteriorated. Furthermore, an increase
of a dark current causes a problem that the accuracy of the voltage
detection can not be sufficiently obtained. In the flying capacitor
technique as disclosed in Japanese Laid-open Patent Application No.
2002-156392, a high voltage section on the battery side and a low
voltage section connected to a ground potential of a vehicle body
are electrically insulated from each other so that elements need to
be provided with voltage resistance in both directions. Therefore,
a large number of elements having high voltage resistance in both
directions are necessary, which results in the increase of the
cost. Furthermore, in above-mentioned Japanese Laid-open Patent
Applications Nos. 2002-156392 and 2002-122643, a switch is changed
over to input a voltage in a common microcomputer and a common A/D
converter. However, such configuration is likely to be affected by
noises due to parasitic capacity or the like. With the
configuration disclosed in Japanese Laid-open Patent Application
No. 2002-122643 wherein a voltage is measured by using a grounded
vehicle body as a reference, a reference potential of a battery
assembly and a potential of a vehicle body are electrically
insulated from each other. Therefore, there easily occurs a noise,
a cause of which is difficult to determine, and the configuration
is likely to be affected by parasitic noises.
SUMMARY OF THE INVENTION
In order to solve the above problems, the present invention has an
object of providing a battery voltage measurement circuit, a
battery voltage measurement method, and a battery electric control
unit wherein a voltage of each of unit batteries constituting a
battery assembly can be measured with high accuracy by using a
common measurement circuit in a relatively simple and inexpensive
configuration.
According to the first aspect of the present invention, there is
provided a battery voltage measurement circuit that measures a
voltage between both electrodes of each unit battery in a battery
assembly having a plurality of unit batteries which are connected
in series. The battery voltage measurement circuit comprises a
conversion unit that is provided with each unit battery and
converts a voltage between both electrodes of the unit battery into
a predetermined physical quantity, and a common measurement unit
that processes and measures the physical quantity converted by the
conversion unit with respect to each unit battery.
With this configuration, it is possible to provide a battery
voltage measurement circuit capable of measuring a voltage in a
simple and easy manner, wherein voltages are measured in a common
unit by using a converted physical quantity which can be easily
processed.
According to the second aspect of the present invention, there is
provided a battery voltage measurement circuit wherein the
measurement unit includes an A/D conversion unit that converts the
voltage between both electrodes of the unit battery into a
corresponding digital signal.
With this configuration, it is possible to convert the voltage into
a digital value, which can be directly measured by computing, by a
relatively simple and inexpensive measurement unit, and process the
measurement easily.
According to the third aspect of the present invention, there is
provided the battery voltage measurement circuit further comprising
a level shifting unit that is provided with the conversion unit and
converts the physical quantity converted by the conversion unit
into a voltage on a reference potential of a lowest electric
potential of the battery assembly. In the battery voltage
measurement circuit, the measurement unit sequentially outputs
digital values corresponding to voltages on a reference potential
of a lowest electric potential of the battery assembly with respect
to each unit battery.
With this configuration, because a voltage between both electrodes
of each unit battery is converted into a voltage on a reference
potential of the lowest electric potential of the battery assembly,
it is possible to sequentially measure voltages with high accuracy
by a single and common measurement unit.
According to the fourth aspect of the present invention, there is
provided the battery voltage measurement circuit wherein the
conversion unit that corresponds to each of the unit batteries is
formed into groups consisting of the predetermined number of the
conversion units, which are adjacent to each other; each group is
provided with a charge pump circuit; and the conversion unit in
each group operates with a power supply from the charge pump
circuit associated with the each group.
It is, therefore, possible to provide a power source, which is
appropriate for an electric potential of a terminal of a unit
battery to be measured, in a relatively simple manner, thereby
facilitating the measurement of a voltage.
According to the fifth aspect of the present invention, there is
provided the battery voltage measurement circuit further comprising
a DC/DC converter that is electrically insulated from the battery
assembly and is used as a power source of each charge pump
circuit.
It is, therefore, possible to provide a stable power source for a
group consisting of the conversion units without being affected by
an output voltage of the battery assembly.
According to the sixth aspect of the present invention, there is
provided the battery voltage measurement circuit wherein the
conversion unit includes a voltage/current conversion unit that
converts the voltage between both electrodes of the unit battery
into a corresponding magnitude of an electric current.
With this configuration, it is possible to convert a voltage in a
relatively simple and inexpensive conversion unit, and a
level-shifting process and a measurement process can be easily
performed.
According to the seventh aspect of the present invention, there is
provided the battery voltage measurement circuit wherein the
conversion unit includes a voltage/frequency conversion unit that
converts the voltage between both electrodes of the unit battery
into an alternating signal having a corresponding frequency.
With this configuration, it is possible to convert a voltage in a
relatively simple and inexpensive conversion unit, and a
level-shifting process and a measurement process can be easily
performed.
According to the eighth aspect of the present invention, there is
provided the battery voltage measurement circuit further
comprising: a control operation unit that is electrically insulated
from the battery assembly; and a transmitting unit that
electrically transmits the digital value corresponding to the
voltage between both electrodes of the unit battery from the
measurement unit into the control operation unit while keeping
insulation between the battery assembly and the control operation
unit.
With this configuration, the insulation between the battery
assembly and the control operation unit can be maintained, and
therefore there is no possibility that the control operation unit
is affected by the battery assembly, thereby improving the
reliability of the control operation unit.
According to the ninth aspect of the present invention, there is
provided a battery voltage measurement method in a battery voltage
measurement circuit that measures a voltage between both electrodes
of each unit battery in a battery assembly having a plurality of
unit batteries which are connected in series. The battery voltage
measurement method comprises the steps by the battery voltage
measurement circuit of: (a) differentially amplifying a voltage
between both electrodes of each unit battery; (b) converting an
output voltage obtained in the step (a) into a predetermined
physical quantity; (c) level-shifting the physical quantity
converted in the step (b) into a voltage on a reference potential
of the lowest electric potential of the battery assembly; and (d)
measuring the voltage, which is level-shifted in the step (c), by a
common measurement unit with respect to each unit battery.
A voltage between both electrodes of the unit battery of the
battery assembly is level-shifted into a voltage on a reference
potential of the lowest electric potential of the battery assembly,
and therefore it is possible to measure a voltage by a single and
common measurement unit having voltage resistance on one side,
thereby facilitating the battery voltage measurement.
According to the tenth aspect of the present invention, there is
provided a battery electric control unit (ECU) that measures a
voltage between both electrodes of each unit battery in a battery
assembly having a plurality of unit batteries which are connected
in series. The battery ECU comprises a processing unit
incorporating: a differential amplification unit that is provided
with each unit battery and detects a voltage between both
electrodes of the unit battery through an input unit to output a
detected voltage; a conversion unit that is provided with each
differential amplification unit and converts the detected voltage
from the differential amplification unit into a predetermined
physical quantity; a level shifting unit that level-shifts the
physical quantity converted by the converter into a voltage on a
reference potential of a lowest electric potential of the battery
assembly; and a measurement unit that measures the voltage
level-shifted by the level shifting unit.
A voltage between both electrodes of the unit battery of the
battery assembly is level-shifted into a voltage on a reference
potential of the lowest electric potential of the battery assembly,
and therefore it is possible to measure a voltage by a single and
common measurement unit having voltage resistance on one side,
thereby facilitating the battery voltage measurement.
According to the eleventh aspect of the present invention, there is
provided the battery ECU wherein the processing unit is an
integrated circuit.
It is, therefore, possible to reduce the size of the battery
ECU.
According to the present invention, a voltage between both
electrodes of each of unit batteries constituting a battery
assembly is level-shifted to a voltage on a reference potential of
the lowest electric potential of the battery assembly, thereby
making it possible to measure a voltage by using a single and
common measurement unit having voltage resistance on one side. It
is, therefore, possible to measure a voltage of each unit battery
of the battery assembly with high accuracy in an inexpensive
configuration without reducing the safety.
BRIEF DESCRIPTION OF THE DRAWINGS
The object and features of the present invention will become more
readily apparent from the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a schematic block diagram of a battery voltage
measurement circuit according to an embodiment of the present
invention;
FIG. 2 is a block diagram of a battery voltage measurement circuit
employing a voltage/frequency converter according to an embodiment
of the present invention;
FIG. 3 is a block diagram of a battery voltage measurement circuit
employing a voltage/current converter according to an embodiment of
the present invention;
FIG. 4 is a block diagram of a battery electric control unit
according to an embodiment of the present invention; and
FIG. 5 is a block diagram of a conventional battery electric
control unit.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described
in detail with reference to the attached drawings.
The same components will be denoted by the same references in the
drawings.
FIG. 1 is a schematic block diagram of a battery voltage
measurement circuit according to an embodiment of the present
invention. In FIG. 1, the reference marks V, A, and T are
accompanied by characters for their identification. When K
(integral number) and a number added to or subtracted from K are
accompanied by the reference marks V, A, and T, the characters are
indicated in parenthesis after K. The reference mark E denotes a
battery assembly that is an object to be measured. The reference
marks V1, . . . , V(K), . . . denote individual unit batteries
constituting the battery assembly E. The reference marks A1, . . .
, A(K), denote differential amplifiers (AMP) that detect a voltage
of each of the unit batteries V1, . . . , V(K), . . . . The
reference marks T1, . . . , T(K), . . . denote converters that
convert an output of each of the differential amplifiers A1, . . .
, A(K), . . . into a predetermined physical quantity. The reference
number 1 denotes a detection circuit that inverts the physical
quantity converted by each of the converters T1, . . . , T(K), . .
. into an electronic signal on a reference potential of the lowest
electric potential of the battery assembly E. The electronic signal
is, for example, a direct-current signal having a voltage that
corresponds to an output voltage of each of the unit batteries V1,
. . . , V(K), . . . , or an alternating-current signal having a
frequency that corresponds to an output voltage of each of the unit
batteries V1, . . . , V(K), . . . . The electronic signal is
hereinafter referred to as a converted signal. The reference number
2 denotes a control unit on a high-voltage section, and the control
unit has a multiplex function and an A/D conversion function. The
multiplex function is used to sequentially output the converted
signals in the order which begins from a converted signal that
corresponds to the lowest unit battery of the battery assembly E. A
converted signal, which is output from the detection circuit 1,
corresponds to a voltage of each of the unit batteries V1, . . . ,
V(K), . . . . The A/D conversion function is used to convert an
input converted signal into a digital signal representing a value
that corresponds to a voltage or a frequency of the converted
signal. The reference number 3 denotes an isolation buffer circuit
that transmits a signal output from the control unit 2 to a
low-voltage section. A signal from the control unit 2 is
transmitted to a control operation unit, which is connected to a
grounded vehicle body, via the isolation buffer circuit 3, and is
then processed. The control operation unit will be described
later.
The converter T is included in a conversion unit set forth in the
claims. The detection circuit 1 includes a function of a
level-shifting unit in the claims and the control unit 2 includes a
function of a measurement unit in the claims.
With reference to FIG. 1, a description will be given on basic
operations of the battery voltage measurement circuit according to
an embodiment of the present invention.
A voltage between both terminals of each unit battery V is
amplified by the differential amplifier A, and is then converted by
the converter T into a predetermined physical quantity that
corresponds to the voltage between both terminals of the unit
battery V. The physical quantity, which is converted by the
converter T, is level-shifted by the detection circuit 1, and is
converted into a voltage on a reference potential of the lowest
electric potential of the battery assembly E.
Thus, an output voltage from the detection circuit 1, which has
been level-shifted to a voltage on a common reference potential,
corresponds to the voltage between both terminals of the unit
battery V. The control unit 2 sequentially selects the
above-mentioned output voltages, which respectively correspond to
the voltages between both terminals of the unit batteries V, by a
multiplexer, converts the voltages by an A/D conversion to generate
serial digital signals, and then transmits the serial digital
signals to the control operation unit via the isolation buffer
circuit 3 such as a photo-coupler.
The physical quantity converted by the converter T must correspond
to a potential difference between both terminals of each unit
battery V. However, the converted physical quantity may be
irrelevant to an electric potential of each terminal of the unit
battery V. Therefore, the converted physical quantity is
level-shifted by the detection circuit 1, and is then converted
into a voltage on a common reference potential of the lowest
electric potential of the battery assembly E, so that it is
possible to acquire a voltage on a common reference potential of
the lowest electric potential of the battery assembly E, i.e. a
potential of 0 (zero) volt, and that corresponds to a voltage
between both terminals of each unit battery V. That is, it is
possible to acquire a voltage on a reference potential of 0 (zero)
volt. Because there is no variation in the reference potentials of
the unit batteries, output voltages of all the unit batteries can
be measured with high accuracy by using the common detection
circuit 1 and the common control unit 2.
A voltage between both terminals of the unit battery V must fall
within the range between positive and negative voltages of each of
power sources of the differential amplifier A and the converter T.
For this reason, it is necessary to provide a plurality of power
sources with the unit batteries V. For example, a charge pump
circuit may be used as a power source.
FIG. 2 is a block diagram of a battery voltage measurement circuit
employing a voltage/frequency converter as the converter T
according to an embodiment of the present invention. It should be
noted that a voltage/frequency (V/F) converter Tf(K) includes the
differential amplifier A(K) shown in FIG. 1.
With reference to FIG. 2, a description will be given on
measurement operations in this embodiment.
For example, a voltage between both terminals of an unit battery
V(K) is input to the V/F converter Tf(K) through an input
resistance R1, which corresponds to an input unit in the claims,
and is then converted by the V/F converter Tf(K) into a frequency
signal .phi.(fk), which corresponds to the voltage between both
terminals of the unit battery V(K). The converted frequency signal
.phi.(fk) is applied through a capacitor C1 to a termination
impedance C2 connected to the lowest electric potential of the
battery assembly E, so that the frequency signal .phi.(fk) can be
separated from a direct-current voltage on the unit battery V(K)
side. Thereby, voltage signals of the individual unit batteries
with different reference voltages can be easily shifted down to
frequency signals .phi.(fk) on a reference potential of the lowest
electric potential of the battery assembly E.
The input resistance R1 is an example of an input unit set forth in
the claims.
The frequency signals .phi.(f1), . . . , .phi.(fk), . . . , which
respectively correspond to voltages of the unit batteries V1, . . .
, V(K), . . . and have been shifted down as described above, are
sequentially converted by a common frequency/voltage converter
(MUX/FVC) 11 into alternating-current voltage signals, which have
frequencies of f1, . . . , fK, . . . , on a reference potential of
the lowest electric potential of the battery assembly E. The
frequency/voltage converter (MUX/FVC) 11 has an input multiplexer.
The MUX/FVC 11 outputs multiplexed alternating-current voltage
signals, which are then fed into an A/D converter (ADC) 12 to be
converted into digital signals that represent values corresponding
to the frequencies f1, . . . , fK, . . . . Then, the digital
signals are transmitted to the control operation unit 4, which is
placed in a main body and is connected to a grounded vehicle body,
via the isolation buffer circuit 3 such as a photo-coupler.
As described above, frequency signals are converted into voltage
signals by the common frequency/voltage converter 11 having the
input multiplexer (MUX/FVC), and then the voltage signals are
converted into digital signals by the common ADC 12, so that it is
possible to convert detected signals into a series of serial
digital signals, and to reduce the number of elements, including
the isolation buffer circuit 3. Because a detection circuit
including the common MUX/FVC 11 and the common ADC 12 is employed
in the present embodiment, it is possible to reduce the variation
of measurements in the battery channels. The detection circuit may
be regarded as the same as the control unit 2 in FIG. 1.
The V/F converter Tf corresponds to a conversion unit set forth in
the claims. The capacitor C1 and the termination impedance C2
includes a function of a level shifting unit set forth in the
claims, and the MUX/FVC 11, the ADC 12, and the control operation
unit 4 include a function of a measurement unit set forth in the
claims.
Because a reference potential of the V/F converter Tf varies
depending on an electric potential of the unit battery V to be
measured, it is necessary to shift up a reference potential of the
V/F converter Tf depending on an electric potential of the unit
battery V in relation to the lowest electric potential of the
battery assembly E. For this purpose, a charge pump P is used as a
power source.
According to an embodiment of the present invention shown in FIG.
2, the unit batteries V constituting the battery assembly E are
formed into two groups: a lower group consisting of V1, V2, . . .
and an upper group consisting of V(K-2), V(K-1), . . . . The lower
and upper groups have almost the same number of the unit batteries
V. The lower and upper groups are provided with direct-current
power sources B1 and B2, respectively. Further, in both the lower
and upper groups, the unit batteries V are formed into a group
consisting of two adjacent unit batteries V. The bottom groups in
both the lower and upper groups are directly supplied with outputs
of the direct-current power sources B1 and B2, and other higher
groups in the lower and upper groups are provided with the charge
pumps P, which are dedicated to each of the other higher groups.
The charge pumps P in the lower group consisting of V1, V2, . . .
are supplied with the electric power from the direct-current power
source B1, and the charge pumps P in the upper group consisting of
V(K-2), V(K-1), . . . are supplied with the electric power from the
direct-current power source B2.
For example, in the lower group, the V/F converters Tf1 and Tf2 are
supplied with the electric power directly from the direct-current
power source B1, and the V/F converters Tf3 and Tf4 are supplied
with the electric power from the charge pump P11 by using a voltage
raised thereby. Similarly, other V/F converters Tf5, . . . in the
lower group are supplied with the electric power from the charge
pump P12 that is driven by the direct-current power source B1.
Similarly, in the upper group, the V/F converters Tf(K-2) and
Tf(K-1) are supplied with the electric power directly from the
direct-current power source B2, and the V/F converters Tf(K) and
Tf(K+1) are supplied with the electric power from the charge pump
P21 by using a voltage raised thereby.
When the power supply voltage of the V/F converter Tf decreases,
the V/F converter Tf can output an erroneous conversion. Therefore,
it is desirable to provide a circuit for detecting an abnormality
of the power supply voltage, and prevent a false detection by
stopping conversion when an abnormality occurs in the power supply
voltage.
With the above-mentioned configuration, an element used as the V/F
converter Tf, and a switching element and a capacitor used as the
charge pump P need to withstand voltages higher than a voltage of
the battery assembly E. However, an output voltage from the unit
battery V is converted into a signal on a reference potential of
the lowest electric potential of the battery assembly E, and
therefore elements may have voltage resistance in one direction.
Thereby, it is possible to reduce the number of elements and use
more inexpensive elements.
FIG. 3 is a block diagram of a battery voltage measurement circuit
employing a voltage/current converter Ti as the converter T
according to an embodiment of the present invention. In the battery
voltage measurement circuit shown in FIG. 3, the unit batteries V1,
V2, . . . , V(K-1), V(K) (the number of the unit batteries is K)
constituting the battery assembly E are respectively provided with
the voltage/current (V/I) converters Ti1, Ti2, . . . , Ti(K-1),
Ti(K), each including an amplifier on its front stage. To simplify
an explanation, K is an even number here. In the present
embodiment, every two adjacent V/I converters Ti are provided with
one charge pump P. In the embodiment as shown in FIG. 2, the unit
batteries V constituting the battery assembly E are formed into a
plurality of groups, each group is provided with a direct-current
power source, and a bottom group in each group is supplied with the
electric power directly from the direct-current power source.
However, the embodiment shown in FIG. 3 does not employ such a
configuration. In the embodiment in FIG. 3, every two V/I
converters Ti are provided with one charge pump P, and therefore
the circuit includes the charge pumps 1, . . . , PJ (J=K/2), that
is, the number of the charge pumps is K/2. Therefore, two adjacent
V/I converters Ti, which are supplied with the electric power from
the same charge pump P, are shown in one block in FIG. 3, for
instance, the converters Ti(K-1), Ti(K), the converters Ti(K-3),
Ti(K-2), . . . . A high potential side terminal of each unit
battery V(K) (K=1, 2, . . . , K) is coupled to a corresponding
input terminal of a corresponding V/I converter Ti(K) through the
resistance R1(an example of an input unit in the claims), and a low
potential side terminal of each unit battery V(K) is directly
connected to a corresponding input terminal of a corresponding V/I
converter Ti(K). Outputs of the V/I converters Ti(K), Ti(K-1),
Ti(K-2), . . . are connected to a common reference potential, i.e.
the lowest electric potential of the battery assembly E, through
detection resistances R2(K), R2(K-1), . . . , which detect a
voltage by measuring a voltage drop. High potential sides of the
detection resistances R2(K), R2(K-1), . . . are connected to input
terminals of amplifiers A(K), A(K-1), . . . , respectively. Outputs
of the amplifiers A(K), A(K-1), . . . are connected to
corresponding input terminals of an A/D converter 13 having a
multiplexer (MUX/ADC). Outputs of the MUX/ADC 13 are connected to
the control operation unit 4 in a circuit block (referred to as a
low voltage side), which is electrically insulated from the battery
assembly E, through the above-mentioned isolation buffer circuit 3.
The battery voltage measurement circuit shown in FIG. 3 includes a
DC/DC converter 6 and a regulator (REG) 7. The DC/DC converter 6
converts a voltage of an output from the direct-current power
source B on the low voltage side. The REG 7 adjusts an output of
the DC/DC converter 6 to be suitable for a power supply voltage
used in an integrated circuit (IC). The DC/DC converter 6 is mainly
used for driving the charge pumps P(J), P(J-1), . . . . The
references I(K), I(K-1), I(K-2), . . . denote output currents from
the V/I converters Ti(K), Ti(K-1), Ti(K-2), . . . .
In the present embodiment, a voltage between both terminals of the
unit battery V is converted by the converter Ti into an electric
current, and then the electric current is output. The converter Ti
may be regarded as a voltage-controlled current source that outputs
an electric current corresponding to a voltage between both
terminals of the unit battery V. A value of an output current of
the converter Ti is independent from a direct-current potential of
the unit battery V in relation to the lowest electric potential of
the battery assembly E. Therefore, by using an electric current
output from the converter Ti, output voltages of the unit batteries
V having different reference voltages can be easily shifted down to
voltages on a common reference potential of the lowest electric
potential of the battery assembly E.
With reference to FIG. 3, a description will be given on
measurement operations in this embodiment.
A voltage between both terminals of each unit battery V(K) is input
to the V/I converter Ti(K) through the input resistance R1, and is
then converted by the V/I converter Ti(K) into a current signal
I(K) that corresponds to the voltage between both terminals of the
unit battery V(K). The converted current signal I(K) is applied to
the termination resistance (detection resistance) R2(K), which is
connected to the lowest potential of the battery assembly E, so
that the current signal I(K) can be converted into a voltage signal
on a common reference potential of the lowest electric potential of
the battery assembly E. The termination resistances R2 have the
same resistance value.
The converted voltage signals on a common reference potential are
sequentially converted into digital voltage signals by the A/D
converter 13 having a multiplexer function (MUX/ADC), thereby
producing a series of serial digital signals. The series of serial
digital signals are then transmitted to the control operation unit
4, which is disposed on the low voltage side and is grounded to
vehicle body, via the isolation buffer circuit 3.
As described above, the voltage signals are sequentially converted
into the digital voltage signals by the common A/D converter 13
having an input multiplexer (MUX/ADC) to produce a series of serial
digital signals, and then the series of serial digital signals are
transmitted to the isolation buffer circuit 3, so that it is
possible to reduce the number of elements, including the isolation
buffer circuit 3. Further, because the common MUX/ADC 13 is used,
it is possible to reduce the variation of measurements between the
battery channels.
The V/I converter Ti(K) includes a conversion unit set forth in the
claims. The detection resistance (termination resistance) R2(K)
includes a function of a level-shifting unit in the claims, and the
MUX/ADC 13 and the control operation unit 4 includes a function of
a measurement unit in the claims.
An output voltage of the insulated DC/DC converter 6, which
converts a voltage of the direct current power source B on the low
voltage side, is used as a reference supply. The voltage of the
direct current power source B is, for example, level-shifted by the
charge pump P(J), thereby charging an external capacitor C3, which
is used as a power source of the V/I converters Ti(K), Ti(K-1).
Furthermore, an output voltage of the DC/DC converter 6 is adjusted
by the regulator 7 and is used as a power source of common elements
such as the MUX/ADC 13 or the isolation buffer circuit 3.
A power source of the V/I converter Ti is configured as described
above, and the V/I converter Ti is supplied with an electric power
from the direct current power source B to output an electric
current. For this reason, the electric power of the battery
assembly E, which is an object to be measured, is not consumed for
the measurement. Thereby, it is possible to realize high input
resistance of an amplifier incorporated in the V/I converter Ti,
and to reduce a capacity of a low-pass filter to be formed on an
input side in order to remove battery noise. It is, therefore,
possible to reduce the size and the cost.
With the configuration of the present embodiment, an element to be
used as the V/I converter Ti and a switching element and a
capacitor to be used as the charge pump P(J) need to withstand
voltages higher than a voltage of the battery assembly E. However,
because a voltage between both terminals of the unit battery V is
converted into a signal on a common reference potential of the
lowest electric potential of the battery assembly E, elements have
only to withstand a high voltage in one direction, and therefore it
is possible to reduce the number of elements and use more
inexpensive elements. It is also possible to reduce the size and
the cost.
Especially when the V/I converter Ti is used to convert an output
of the unit battery V as described in the present embodiment, a
multiplexer incorporated in the MUX/ADC 13 may have one input
contact for each unit battery V, thereby simplifying the
configuration of the circuit.
In the above-mentioned embodiment, voltages between both terminals
of the unit batteries V are converted into and shifted down to
frequency signals or electric currents, converted into a series of
serial digital signals through a common measurement circuit, and
then transmitted to the control operation unit 4 via the isolation
buffer circuit 3. It is, however, possible to directly convert
voltages between both terminals of the unit batteries V into
digital signals by A/D conversion, and sequentially process digital
signals that correspond to voltages of the unit batteries.
According to another embodiment of the present invention, a brief
description will be given on a battery electric control unit (ECU)
incorporating the above-mentioned battery voltage measurement
circuit of the present invention.
FIG. 4 is a block diagram of a battery ECU 100 according to an
embodiment of the present invention. For comparison, FIG. 5 shows a
block diagram of a conventional battery ECU as described in the
above-mentioned Japanese Laid-open Patent Application Hei.
11-113182. It should be noted that a control unit 42 on a high
voltage side and a control operation unit 4 on a low voltage side,
which are shown in FIG. 4, are replaced by a control unit 52 on a
high voltage side and a control operation unit 54 on a low voltage
side, which are shown in FIG. 5, respectively.
In FIG. 4, a high voltage integrated circuit (HVIC) 21 is
configured by integrating circuits each including converters and
charge pumps. The control unit 42 on the high voltage side has an
inverse transform function, a multiplexer function, and an A/D
conversion function. The isolation buffer circuit 3 includes a
two-way circuit so that the isolation buffer circuit 3 transmits a
measurement data from the control unit 42 on the high voltage side
to the control operation unit 4 on the low voltage side, and the
isolation buffer circuit 3 transmits a control signal from the
control operation unit 4 on the low voltage side to the control
unit 42 on the high voltage side. The DC/DC converter 6 and the
regulator 7 operate in the same manner as mentioned with reference
to FIG. 3.
By integrating input circuits by the HVICs as mentioned above, it
is possible to reduce the number of components having high voltage
resistance, and to reduce the size and the cost. Furthermore, the
whole circuit can be easily integrated, and the battery voltage
measurement functions can be integrated in one battery ECU 100.
A conventional battery ECU shown in FIG. 5 includes a switch
circuit 25 having photo-MOS switch circuits (hereinafter referred
to as channels). The channels of the switch circuit 25 are
sequentially selected in response to a control signal transmitted
from the control operation unit 54 on the low voltage side through
an unshown isolation buffer element. Compared to the conventional
battery ECU shown in FIG. 5, the battery ECU 100 shown in FIG. 4
makes it much easier to configure the circuit, thereby reducing the
number of isolation elements such as the isolation buffer
circuit.
According to an embodiment shown in FIG. 4, the lowest electric
potential of an battery assembly E1, which is configured by unit
batteries V1, V2, . . . , V20 (to simplify an explanation, the
number of the unit batteries is 20), can be used as a common
reference potential. As shown in FIG. 4, it is, therefore, possible
to easily configure detection circuits for detecting an electric
current or a voltage, and to incorporate a battery current
detection circuit (IB) 22 and a precharge contactor (PRECHG) 23
inside the battery ECU 100. The precharge contactor 23 is used for
charging a capacitor in a power supply circuit in advance when an
ignition switch is turned on. Furthermore, a leakage detection
circuit (LEAK) 24 between a high voltage side and a grounded
vehicle body can be simplified and optimized in the configuration
by using the lowest electric potential of the battery assembly E1
as a common reference potential. There is, therefore, an advantage
that it is possible to reduce parts to be isolated in the
circuit.
According to the present invention as described above, a voltage
corresponding to a voltage between both terminals of each unit
battery to be measured is converted into a converted signal, and is
level-shifted to a voltage on a common reference potential. A
voltage is detected by a common measurement unit with high
accuracy, and a detected signal is transmitted as a serial digital
signal to a control operation unit in a low voltage section via an
isolation element. It is, therefore, possible to achieve a battery
voltage measurement circuit that measures a voltage of each unit
battery of a battery assembly with high accuracy in an inexpensive
configuration without reducing the safety.
In the above description, examples of embodiments have been given
to explain the present invention. It is, therefore, easy for a
skilled person in the art to make various changes, modifications or
additions in the above embodiments within the scope of the
technical idea and the principle of the present invention.
For example, the above explanation has been given to mainly
describe a battery voltage measurement circuit. However, the
present invention should include a battery voltage measurement
method to be used in the battery voltage measurement circuit.
According to the present invention, it is possible to detect a
voltage of each battery such as a unit battery of a battery
assembly during operation with high accuracy by using the smaller
number of components than that of a conventional battery voltage
measurement circuit. The present invention, therefore, can be
widely used in the industry which requires monitoring of a battery
voltage, mainly in the wide range of industries where a fuel cell
is used.
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